ACPAtmospheric Chemistry and PhysicsACPAtmos. Chem. Phys.1680-7324Copernicus GmbHGöttingen, Germany10.5194/acp-5-2357-2005Global satellite validation of SCIAMACHY O<sub>3</sub> columns with GOME WFDOASBracherA.1LamsalL. N.1WeberM.1BramstedtK.1Coldewey-EgbersM.1BurrowsJ. P.11Institute of Environmental Physics and Remote Sensing (IUP/IFE), University of Bremen, Otto-Hahn-Allee 1, 28 334 Bremen, Germany130920055923572368This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.This article is available from http://www.atmos-chem-phys.net/5/2357/2005/acp-5-2357-2005.htmlThe full text article is available as a PDF file from http://www.atmos-chem-phys.net/5/2357/2005/acp-5-2357-2005.pdf

Global stratospheric ozone columns derived from UV nadir spectra measured by
SCIAMACHY (Scanning Imaging Spectrometer for Atmospheric Chartography; data
ESA Versions 5.01 and 5.04) aboard the recently launched Environmental
Satellite (ENVISAT) from January to June 2003 were compared to collocated
total ozone data from GOME (Global Ozone Monitoring Experiment on ERS-2)
retrieved using the weighting function DOAS algorithm (WFDOAS; Version 1.0)
in order to assess the level-2 data (trace gas data) retrieval accuracy from
SCIAMACHY. In addition, SCIAMACHY ozone columns retrieved with WFDOAS V1.0
were compared to GOME WFDOAS for some selected days in 2003 in order to
separate data quality issues that either come from the optical performance
of the instrument or algorithm implementation. Large numbers of collocated
total ozone data from the two instruments, which are flying in the same
orbit about 30 min apart, were spatially binned into regular 2.5&deg;
times 2.5&deg; grids and then compared. Results of these satellite
comparisons show that SCIAMACHY O<sub>3</sub> vertical columns (ESA Version
5.01/5.04) are on average 1% (&plusmn;2%) lower than GOME WFDOAS and
scatter increases at solar zenith angles above 85&deg; and at very low total
ozone values. Results show dependencies on the solar zenith angle,
latitudes, and total ozone amounts which are explained by the implementation
of an outdated GOME algorithm based on GOME Data Processor (GDP) version 2.4
algorithms for the SCIAMACHY operational product. The reprocessing with an
algorithm equivalent to GOME WFDOAS V1.0 shows that the offset and
dependencies on solar zenith angle, latitude, and total ozone disappear and
that SCIAMACHY WFDOAS data are within 1% of GOME WFDOAS. Since GOME lost
its global coverage in July 2003 due to data rate limitation, continuation
of the total ozone time series with SCIAMACHY is of highest importance for
long-term trend monitoring. Since the beginning of its operation in March
2002 the SCIAMACHY instrument has performed stable. With the application of
proper algorithms to retrieve total ozone, SCIAMACHY will be able to
contribute to the global long term satellite total ozone record and it has
the potential to achieve the high accuracy of GOME total ozone.